Field of the Invention
The invention relates to an electromagnetic switching device including at least one moveable contact and an associated drive in a device housing, a device for contactlessly identifying a switching state has at least one magnetic field sensor, is disposed at a suitable location inside and/or outside the device housing and detects magnetic field values each linked to one of a plurality of switching states, and the device housing has a switching handle that is intended for manual release and has a position being monitored.
Switching states of electromechanical protective switchgear are characterized by release operations of a switch mechanism and, accordingly, can be identified by detecting a change in a position of certain components such as, for example, a switching handle of a usually present magnetometer or of an associated bimetal, and an associated occurrence of powerful magnetic fields in the event of overcurrent or short circuit.
German Published, Non-Prosecuted Patent Application DE 197 07 729 A1, provides magnetosensitive sensors such as Differential Hall Effect (DHE) sensors, Giant Magneto Resistive (GMR) sensors and Anisotropic Magneto Resistive (AMR) sensors for the purpose, in particular, of detecting movement of the switching handle of a circuit-breaker from a rotary movement of a drive clip that is coupled therewith.
The above-mentioned DHE, GME and AMR sensors in each case contain integrated electronics and supply normalized output signals. A GMR sensor, in particular, requires an additional differential amplifier. The GMR sensors, in particular, additionally have the peculiarity of deficient stability of sensor properties with respect to magnetic overdriving. Overall, the previously known sensors are comparatively complicated and expensive.
U.S. Pat. No. 4,706,073 discloses an alarm sensor system for an electromechanical switching device in which an iron-containing or non-iron-containing metallic pick-up element is present and constitutes a variable reluctance sensor. In that case, the intention is for the handle of the switching device to be monitored by such a sensor. In the event of release, the handle moves into the release position and transfers the proportion of the magnetic flux to the magnetic field sensor. The flux in the sensor changes and causes a current flow in the wire coil of the sensor. A voltage pulse is generated therefrom as pick-up signal.